1. Field of the Invention
The present invention relates to a high pressure rapid cutting tip nozzle suitable for use in gas cutting a thick steel plate, such as in continuous strands gas cutting machines. This application is based on patent application No. Hei 9-361519 filed in Japan, the content of which is incorporated herein by reference.
2. Description of the Related Art
Previously, the present inventors proposed a high pressure rapid cutting tip nozzle (referred to hereinbelow as a "tip nozzle") disclosed in Japanese Utility Model, No. Hei 5-39293. This tip nozzle provides, from the inside around the cutting oxygen jet hole positioned at the center, a first oxygen jet hole group, a first fuel gas jet hole group, a second fuel gas jet hole group, and a second oxygen jet hole group or an oxygen jet opening, so as to form concentric circles centered on the cutting oxygen jet holes. In addition, in order to increase the heating effect, between adjacent fuel gas jet holes, oxygen jet holes which branch from the flow path leading to the oxygen jet holes are provided.
When cutting steel, the high pressure cutting oxygen jet flow from the cutting oxygen jet hole jets out at a high speed, and a first heating flame group is formed from the jetting oxygen and the fuel gas which jets out so as to surround it. In addition, a second heating flame group is formed around the first heating flame group. Additionally, from the multiplicative effect of these heating flame groups, in particular the first heating flame group which covers the cutting oxygen jet flow, is extended and maintained. As a result, the jet effect of the cutting oxygen jet flow jetting from the cutting oxygen holes is increased, and highly efficient gas cutting can by carried out even on thick steel.
However, the tip nozzle of Japanese Utility Model, No. Hei 5-39293 mixes the fuel gas and oxygen at the nozzle end, using a mixing system called out mixing (also called post mixing). Because the fuel gas and oxygen are mixed outside the tip nozzle, the mixing rate of this system is rather low compared to torch mixing, carried out in the blow pipe on which the tip nozzle is installed, and tip mixing, carried out in the tip nozzle, and therefore, there is a tendency for the burn efficiency to deteriorate.
However, the flame of the gas from igniting the mixed gas used in a gas cutter has a temperature exceeding 3000.degree. C., and jets very rapidly. Because of this, if the flow is blocked due to cutting slag, etc., during cutting, the flame runs up the tip nozzle and the blow tube, and there is the problem of causing what is called a back fire or a flash back. Thus, taking this into account, particularly in gas cutting thick steel which consumes fuel gas or oxygen in a high volume, out mixing is generally used.
In consideration of the above, it is the object of the present invention to mix fuel gas and oxygen satisfactorily and improve the cutting efficiency while paying attention to safety in a tip nozzle of an out mixing system.